Losses and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reserves For Losses And Loss Adjustment Expenses [Line Items]
Unpaid claims and claim adjustment expenses overall development	$ 1,200	$ 2,150	$ 2,825	$ 7,702
Accidental Year 2017,2015 and Prior [Member]
Reserves For Losses And Loss Adjustment Expenses [Line Items]
Unpaid claims and claim adjustment expenses overall development	$ 1,200
Accidental Year 2019 and Prior [Member]
Reserves For Losses And Loss Adjustment Expenses [Line Items]
Unpaid claims and claim adjustment expenses overall development			2,825
Accidental Year 2020 [Member] \| Hurricane Sally [Member]
Reserves For Losses And Loss Adjustment Expenses [Line Items]
Unpaid claims and claim adjustment expenses overall development			$ 17,700